Re: Proposal for key wrap/unwrap (ISSUE-35)

On Fri, Mar 1, 2013 at 9:53 AM, Vijay Bharadwaj
<> wrote:
> I've been looking at key wrap formats lately. My observations based on having maintained crypto APIs:
> 1. More wrapping formats means more confusion for developers and pain for vendors.
> 2. Having wrapAlgorithm be a separate option on the import interface leads to various opportunities for inconsistency, since key wrapping formats include varying amounts of metadata. It is better to have import only deal with formats that are self-describing.
> So given that we generally look to JOSE for high-level formats, I'd like to propose using JWE encapsulation for the wrap/unwrap formats, and removing the wrapAlgorithm parameter (and perhaps keyAlgorithm, though this needs more thought) from createKeyImporter in Mark's proposal.
> A good starting point seems to be the JWE-protected JWK I-D at
> Three simple example usages of this format to illustrate what I expect will be the most common use cases:
> 1. For RSA wrapping: Proceed as in Section 5 of the above I-D. JWE header has alg set to RSA-OAEP, and jwk.kty set to RSA. Most people would likely use enc of A128CBC+HS256 or A128GCM.
> 2. For wrapping a key using AES: JWE header has alg set to dir, and enc as in #1. In this case the jwk element in the header is not necessary. This allows the use of any authenticated encryption mode, not just AES key wrap. This seems to be in line with the current consensus of the cryptographic community - NIST has also Approved the use of authenticated encryption modes for key wrapping:
> 3. For working with existing legacy formats such as PKCS#8: JWE header has alg set to dir, and enc set to the appropriate value (e.g. "pkcs-8" in this case).
> The nice thing about this mechanism is that it's web-developer friendly, and adds minimal overhead for the case of the legacy formats.
> Thoughts? If people are okay with the general idea, I can work with Mark to revise the proposal as per our action item from the last meeting.

Mark's proposal was an update to the import/export key semantics.

Do you also see making the proposal that we only support JWK for key
import/export? If so, according to the Miller draft (and to JOSE, from
the last IETF), only protected keys should be supported. How would you
propose to support unprotected/non-JWE-protected keys - which are a
valid and important use case? Setting "enc" to "dir" doesn't mean
unprotected. Perhaps you meant setting the JWK alg to some form (eg:
'pkcs8') ?

Received on Friday, 1 March 2013 18:25:58 UTC